Power Entry module (Twin fused?)

[makinrose]

Mains fuse protects the power transformer against high current draw. Unfortunately, a single fuse is pretty poor protection---sometimes by the time it blows parts of the amp can be damaged. That's why more modern amps have additional fusing so that those fuses can protect individual windings on the transformers and better protect the amp. If you are building kits, you'd do well to add some more fusing....kit companies often copy old amps warts and all. Heck I've seen quite a few kits that don't even update amps to have a bias pot.